1. Field of the Invention
The present invention relates to a method and apparatus for recording and/or reproducing information in a high density and with a large capacity using a probe electrode, and to an information recording carrier suitable for use in the method.
2. Description of the Related Art
Recent applications of memory elements and memory systems are diverse to computers and associate instruments, video disks, digital audio disks, etc., forming a core of electronics industries. Conventionally leading memories were magnetic memories and semiconductor memories. There have been, however, appearing optical memory elements using inexpensive, high density recording medium with recent progress of laser technology. It is highly desired to embody a memory device or method with a large capacity, but in a small volume for future development of computer utility at home and of information industry directed to images.
Meanwhile, a scanning tunnel microscope as referred to as STM has recently been developed which can directly observe an electronic structure of surface atoms of a conductor (G. Binn et al., Helvetica Physica Acta., 55. 726 (1982)). The STM allows one to observe a single crystal and an amorphous substance in a real space with a high resolving power. The STM uses such a principle that a tunnel current flows when a metal probe approaches a conductive material up to a distance of about 1 nm with application of voltage between them. The tunnel current is very sensitive to a change in distance between them. Then, manipulating the probe to maintain the tunnel current constant, one can obtain an image of surface of real space. The observation with the STM has been limited to conductive materials, but has already been started applying to an analysis of structure of a thin insulating film formed on a surface of conductive material. Further, since the STM uses a micro current for detection, it is advantageous in observation without any damage on a material to be observed and with a low power. Also, the STM can be operated in air or in solution as well as in ultra high vacuum, and therefore is applicable to various materials, with an expectation to broaden its applications.
Another application of the STM is an Atomic Force Microscope as referred to as AFM (G. Binnig et al., Phys Rev. Lett., 56, 930 (1985)). The AFM also allows one to obtain information about unevenness of surface as does the STM. Since the AFM can measure an insulating specimen on an order of an atom, further development is expected in future.
Recently, there have been proposed apparatuses applying the principles of the STM and AFM such as a recording apparatus for writing information with high resolving power and reproducing apparatus for reading out the recorded information with high resolving power. In the apparatus applying the STM and AFM technology, since it is necessary to control a distance between the probe electrode and the recording medium up to about 1 nm, the technology for controlling the distance with precision is required.
In the prior art to apply the principle of the STM and AFM, it was required to provide complicated control circuit and mechanism for controlling the distance between the probe electrode and the surface of the recording medium with order of nm. Further, in case of providing a plurality of probe electrodes for the sake of improvement of the recording and reproducing processing, preferable technology for controlling the distance between each electrode and the surface of the recording medium was required.